PROJECT SUMMARY/ABSTRACT Approximately 50 million people worldwide are blind and ~150 million are significantly vision impaired. Except for trauma and infections, the majority of human eye diseases are genetic in nature. The number of human loci causing retinal disease is ~ 9-fold greater than the number of available associated animal models, indicating a large gap in models for studying diseases that are known to occur in humans. The mouse with its well-developed genetics, similarity to human physiology and anatomy, and accessibility for genetic manipulation is a widely accepted and useful model system. Mouse models have been used to provide candidate genes for human diseases, tissues for study throughout development and disease progression, and test systems for therapies. They are also an ideal platform to identify and dissect biologically relevant pathways through genetic means. In the last funding cycle, we generated >60 models with ocular defects. We have identified the molecular basis of 20 of the mutant lines from which many unique insights were obtained. In this application, we plan to complete the molecular and phenotypic characterization of the 40 remaining lines (Aim 1) and make them available to the scientific research community. Extending our ongoing genetic studies, we propose to use a sensitized chemical mutagenesis screen to reveal pathways important in the Crumbs1 pathway (Aim 2). While there are many strategies available to identify interacting factors of primary genes/mutations, chemically induced mutations have the advantage that they will allow for the unbiased identification of a wide array of genes that interact with CRUMBS1. These genes may explain the plethora of diseases associated with mutations within Crumbs1. It will also allow for identification of factors that interact with the extracellular domain of CRUMBS1, an endeavor that has been intractable by the current available methods. In the present application, we will screen ~10,000 mutagenized G3 Crumbs1rd8/rd8 mice by indirect ophthalmoscopy to identify mutants that present with an altered Crumbs1drd8 fundus phenotype. The molecular bases of these factors will be identified and through the use of standard immunohistochemical methodologies in conjunction with the use of 4Pi microscopy, we will examine the effects of the newly identified genes/mutations on the CRUMBS1 pathway. Successful conclusion of this proposal will not only generate well characterized ocular models, but will potentially identify entry points into the CRUMBS1 pathways as well as other molecules that are important in eye biology and afford us the opportunity to build and test hypotheses about normal ocular function and disease pathology.